How to add a specularity map in cycles?
Do it just like blender guru. To do this see image:



To be more specific, Cycles is a unbiased ray tracing engine. That means that computer actually computes the rays of light in the scene. Because of this the specularity of a material is not controlled by a setting, but by the actual physical properties that create the effect. For this reason their is no specularity setting. 

The reason why some render engines have a control for specularity is because they fake the effect.